Microsoft on Monday added a new rent-not-own software subscription plan to a pair of everything-and-the-sink deals it introduced this summer, taking aim at an enormous pool of potential customers that dwarfs the typical office crowd it's targeted for decades.

The plan, another under the "Microsoft 365" label, is designed for what the company dubs "firstline" workers - the employees on the front lines of their organizations, those who ring up sales, take calls, interact with customers and spend their hours on factory floors or in the field.

Few have a work-related digital device. And Microsoft wants to change that.

"We see an opportunity for technology to give Firstline Workers a more intuitive, immersive, and empowering experience," said Bryan Goode, an Office 365 general manager, in a post to a company blog yesterday.

With the Microsoft 365 F1 subscription, Microsoft hopes to bring millions more users under its operating-system-and-productivity-applications dominance.

That is, if we can figure out what F1 is and what's in it.

What's in Microsoft 365 F1? The new subscription plan includes:

Office 365 F1: The foundation of what was formerly known as "Office 365 K1," with the "K" for "kiosk," is Office Online, a web-based set of apps featuring scaled-down, browser-accessed versions of Word, Excel, PowerPoint, OneNote and others. Email is handled by the Outlook website at outlook.com. Office Online is free for non-commercial purposes, but requires an Office 365 subscription of some kind to be legally used in the workplace.

A license for Windows 10 Enterprise, the top-tier version that Microsoft deals to corporate customers. [More on this later.]

Enterprise Mobility + Security (EMS), a collection of device- and user-management services and tools, combined with a set of advanced security features and services. EMS includes Intune, Microsoft's cloud-based management platform, and Azure Active Directory (AAD), also cloud-based, for user sign-on and authentication.

How much does M365 F1 cost? $10 per user per month when it launches, which looks to be scheduled for next month.

That's $6 per user per month more than Office 365 F1, the subscription once known as "Office 365 K1," or an additional $72 annually. (It's also half the price of the $20 per user per month for Microsoft 365 Business, the previous lowest-priced plan in the line.) For the extra money beyond Office 365 F1, customers receive a license for Windows 10 Enterprise and the tools and services under the EMS umbrella.

Who is Microsoft 365 F1 for? According to Microsoft, the plan targets the employees who "are the first to engage customers," and who, unlike so-called knowledge workers, spend the vast bulk of their work hours away from a personal computer. Instead, they are "the people behind the counter, on the phone, in clinics, hospitals, and on the shop floor."

Companies of any size can purchase M365 F1 licenses, including those already paying for other Microsoft 365 plans, such as Business, Enterprise E3 or Enterprise E5.

In fact, Microsoft told reselling partners that they will have the best luck "with customers that are already using Microsoft 365," adding that "M365 customers are 2x as likely to attach Firstline Worker services" than those that haven't yet tried Microsoft's most expensive subscription packages.

What does Microsoft 365 F1 require? According to Microsoft's circular argument, "A Microsoft 365-powered device is the best way to experience Microsoft 365 F1."

And what's a "Microsoft 365-powered device?" That's "a PC with Windows 10 Enterprise and Office 365 ProPlus, managed with Enterprise Mobility + Security (EMS)." (Actually, that definition is slightly off in F1's case, since it runs Office Online, not the locally-stored, more ambitious versions of applications such as Word, Excel and PowerPoint.)

But Microsoft also plugged less-expensive, Windows 10 S-powered hardware as suitable for F1 and its users. "We recognize the importance of providing Firstline Workers streamlined and secure devices that minimize total cost of ownership," Bryan Goode, a general manager with the Office 365 group, said in a post to a company blog. Goode then introduced new PCs from Acer, Hewlett-Packard and Lenovo that run Windows 10 S - the locked-down edition that permits only Universal Windows Platform apps - as "ideal for firstline environments."

What Windows 10 does F1 license to users? In its online materials to partners, Microsoft simply labels it "Windows 10 Enterprise," the most expensive SKU (stock-keeping unit) in its portfolio and the same as is licensed by pricier subscriptions such as the $20 per user per month Microsoft 365 Business.

But the company also said that F1's OS license isn't the same as the real Windows 10 Enterprise. "The edition of Windows 10 Enterprise and the combination of Enterprise Mobility + Security components ... in Microsoft 365 F1 are unique to this offering and cannot be purchased as standalones [emphasis added]," the company told partners in a FAQ.

That mouthful - Windows 10 Enterprise in S Mode - was mentioned several times in materials promoting F1 as well as in the announcement of new Windows 10 S notebooks coming from OEMs like HP and Lenovo. In the latter, Windows marketing manager Bernardo Caldas said, "With the new Windows 10 Enterprise in S mode, customers will be able to experience Windows 10 Enterprise with all the benefits of Windows 10 S" after a future update if they also subscribed to M365. Doing so, Caldas added, would furnish some of the same security and management features provided to M365 F1.

Although it's unclear whether the Windows 10 Enterprise license bundled with F1 is locked down in the same way as Windows 10 S - meaning it can access only those apps offered in the Windows Store - it is apparent that it's not the full Enterprise as corporate IT professionals understand it.

Only some of the advanced features and tools normally included in Enterprise are available in the OS offered with F1. Credential Guard is, for instance, but Windows Advanced Threat Protection (ATP) is not. From all indications, F1's Windows 10 Enterprise has most of what's included with the license offered to M365 Enterprise E3 subscribers.

Computerworld found another sign that the Windows 10 Enterprise included with F1 is not the same as Windows 10 Enterprise in S mode. The partner FAQ pointed out that several components of the former - Microsoft Advanced Threat Analytics and Credential Guard, for example - are not available in the latter.

What's Microsoft after with M365 F1? Money. Potentially, a lot of money.

The company told partners that their opportunities in the "firstline" market are enormous. "A study commissioned by Microsoft shows that there are ~690 [million] Firstline Workers in enterprise organizations with 500+ employees," the company told resellers.

In the same presentation, Microsoft made it even plainer. "The size of the Firstline Worker employee base is significantly greater than the corresponding number of knowledge workers within these organizations and we have only scratched the surface of capitalizing on this very significant opportunity," the firm contended.

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